To enable radio communication between a railroad train operating on a train track and an operation command room, for example, on the ground, a train radio system serving as one type of mobile communication system is provided. The train track can be macroscopically considered as one line, and can be considered as two lines close to each other when it needs to be distinguished for each operation direction in a double-track section. Therefore, it is considered that the train radio system may target a region represented by such lines. Thus, the train radio system is generally configured by installing a long or lengthy antenna such as a leaky coaxial cable (LCX) close to a train track and along the train track and connecting a base station to this antenna while arranging an on-board device in the train. The LCX is also referred to as a leaky feeder. In the train radio system using the LCX, a radio wave, which has leaked from the LCX installed along the train track, is received on the train (i.e., an on-board device), to enable communication between the ground side and the train. The LCX is also used as a measure against a neutral zone, which radio waves do not reach, such as a tunnel when a mobile phone service is provided. Note that a train radio system targeting a region having an extent as a plane may also be provided depending on a geographic arrangement of the train tracks.
This type of mobile communication system is configured to supervise base stations in a central control apparatus by arranging base stations with spacing of several kilometers along a route when the route is long, then connecting an LCX to each of the base stations, and connecting the base stations and a central control apparatus to each other via a wired cable. If the spacing between the base stations is longer than the length of a section covered by the one LCX, a plurality of LCXs are arranged along the route, and then each of the LCXs and the base station can also be connected to each other via a relay cable.
To stably operate the mobile communication system represented by the train radio system, it is necessary to quickly detect the occurrence of a failure or a fault in the LCX and the base station connected to the LCX, and then specify the fault site. However, to detect the failure or the fault to specify the fault site, field investigation is generally required, and this requires an enormous cost and time. PTL 1 discloses that a detection sensor including a loop antenna is moved along an LCX to detect a fault from a leakage magnetic field intensity or a leakage electric field intensity as a method of detecting a position of a crack, a fracture, or the like in its initial stage in the LCX with high accuracy. The method discussed in PTL 1 requires an investigator to move with a loop antenna in hand, and eventually requires field investigation by the investigator.
PTL 2 discloses a method of detecting a failure in a transmission line such as an LCX laid along a road or the like, wherein the method enables communication among ground stations (i.e., base stations) by a network, provides a failure detector that monitors an output radio wave from the adjacent ground station at each ground station, and detects the failure particularly based on a change in transmission loss in the transmission line.